| 摘要 |
PURPOSE:To produce a Zn alloy plated steel sheet having the excellent corrosion resistance of the plating layer as well as corrosion resistance and painting adhesiveness after painting by electroplating a specifically composed Zn-Fe-Co alloy on the surface of a cold rolled steel sheet. CONSTITUTION:The cold rolled steel sheet is cleaned by degreasing and pickling and is then subjected to plating of the Zn-Fe-Co alloy in a plating bath constituted in the following way: The plating liquid prepd. by dissolving water soluble zinc sulfate, iron sulfate and cobalt sulfate respectively as ion sources for Zn, Fe and Co in water to contg. >=50g/l total of Zn<2+>+Fe<2+>+Co<2+>, <=1 ratio of Zn<2+>/(Fe<2+>+Co<2+>) by weight and 5-50 ratio of Fe<2+>/Co<2+> by weight is used and the steel sheet as a cathode is electroplated in such plating liquid at 20-100A/dm<2> current density. The steel sheet having not only excellent bare corrosion resistance as well as excellent paintability such as corrosion resistance and paint adhesiveness after painting is thus obtd.
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